The invention concerns a method for locating a large number of fibre ends in a bundle of optical waveguides, in particular glass, quartz or synthetic fibres, into a number of pre-determined positions and a method for producing a glass, quartz or synthetic fibre end which can be coupled with a plug-in device.
In the case of optical fibre cables with a large number of optical fibres it has previously been customary to grip the individual fibres manually and to locate them individually in a pre-determined position.
In this manner for instance, optical fibres lying side by side could be arranged in a uni-dimensional array and coupled with the plug-type connection of an optical fibre cable.
A disadvantage of a procedure of this nature is that this procedure for positioning many glass, quartz, or synthetic fibres accurately is extremely time-consuming and costly.
In particular, a method such as this did not allow a two-dimensional optical fibre array with, for instance, 2xc3x972 to 40xc3x9740 optical fibres to be located in a plug connector in such a way that an optical fibre cable with a large number of optical fibres could terminate in a two-dimensional matrix, which is for instance quadratic or rectangular. In particular, the methods representing the current state of the art did not allow exact positioning within a range of just a few micrometers (xcexcm) of a very large number of optical fibre ends with minimal spacing.
The aim of the invention is thus to provide a method with which these disadvantages can be overcome, and in particular a method which makes very accurate positioning in a two-dimensional matrix possible with the distance between fibre ends being only a few xcexcm.
In particular, this method is designed to simplify the point-to-point alignment of two optical fibre ends. Moreover, the method is designed to allow the manufacture of fibre optic cables to be largely automated.
In accordance with the invention this is achieved by bringing the ends of the fibres in contact with a fixing device encompassing a large number of apertures for the ends of the fibres and by moving the fixing device or the ends of the fibres or the fixing device and the end of the fibres in such a way that the ends of the fibres protrude through the aperture of the fixing device as a result of the movement and therefore reach the position pre-determined by the apertures, for instance, within a two-dimensional matrix.
The advantage of such a solution is in particular that the individual fibres can be positioned in extreme proximity to one another, due to the fact that by using such a method very narrow spacings, such as those pre-determined for instance by the width of the spacers in the fixing device, do not present any problems in terms of the positioning.
By using the method in accordance with the invention, the ends of optical fibres can be positioned with  less than xc2x12 xcexcm accuracy, with the individual optical fibres comprising core, cladding and protective sheath capable of having a diameter 20 xcexcm, especially of 100 xcexcm to 1000 xcexcm especially 260 xcexcm. The stripped ends of the optical fibres, without their protective sheath and consisting of core and cladding, can have a diameter ranging from 50 to 800 xcexcm.
It is particularly advantageous if the ends of the optical fibres and/or the fixing device are/is moved periodically, and in particular caused to oscillate. This can occur for instance by means of vibration.
A possible embodiment of the fixing device consists in its configuration as an apertured plate, with the individual apertures being formed by the spacers which are separated by a fixed distance.
In the case of an apertured plate of this kind it is advantageous if the distance between the spacers separating the individual apertures is selected in such a way that precisely only one single end of a fibre can fit through the aperture.
As an alternative to a fixing device with fixed pre-determined aperture dimensions, it is also possible to create a fixing device which provides for the size of the apertures to be varied within a pre-determined range by means of flexible spacers. A fixing device of this type allows the individual fibres to be initially inserted into relatively wide apertures. However, the width of these apertures may only be chosen such that they only just prevent the entry of a second fibre. The size of the apertures is reduced after the individual fibres have been inserted in order to position the individual fibres accurately.
A solution of this nature has the advantage over and above the fixed matrix that it is virtually impossible for individual fibres not to pass through the apertures, making it unnecessary to reposition them in a time-consuming and expensive follow-up process in the usual manner.
Another advantage lies in the fact that the optical fibres can also be fed through several such fixing devices, with the width of the apertures of the individual fixing devices being individually adjustable.
In particular, the advantage lies in the fact that by inserting the fibres through as many plates as possible, the selection involved in the insertion procedures is reduced. In order to isolate individual cables each consisting of two apertured plates, the plates can then be drawn apart.
In addition to the positioning method in accordance with the invention, in particular the invention also provides a method for producing the end of an optical fibre which can be coupled with a plug-in connector and which encompasses a large number of individual optical fibres.
It is only with coupling technology of this kind that it becomes possible to provide an optical fibre cable with a two-dimensional optical fibre array for the manufacturing effort and expense which is justifiable and which could for instance be employed in the field of optical data communication.
The method for manufacturing the end of an optical fibre in accordance with the invention permitting it to be coupled with a connecting device encompasses the stage of positioning the individual optical fibres with the aid of the method in accordance with the invention, the initial attachment of the ends of the fibres, and their positioning and final attachment. The final attachment of the ends of the fibres can be achieved for instance by filling them with a filling compound and then curing. This final attachment can for instance be integrated into a connector plug.
After inserting such an end of an optical fibre cable into a connecting device, it is advantageous for acceptable optical quality for the optical fibres which are now arranged within a two-dimensional matrix to be ground and polished so that an optical fibre array results which is arranged in one plane.
For accurate positioning it is advantageous if the individual optical fibres which are arranged in an optical fibre array do not have a protective sheath, i.e. the ends of the optical fibres consist solely of the optical fibre core and the cladding.
Synthetic material and/or adhesive is preferred as the filling compound.
The invention shall be described below with reference to examples of the embodiments. Although the following examples of embodiments refer to glass optical fibres as the optical waveguides, the method in accordance with the invention can be applied to any other form of optical waveguide, for instance quartz or synthetic fibres without deviating from the invention.